Liquid Fuel Combustion System

ABSTRACT

A liquid fuel combustion system is provided. The system comprises:
         a combustion stove, comprising a vaporization unit with a ring shape vaporization space, a burner assembly and a first pipeline;   a liquid fuel storage tank, having a storage space;   a second pipeline, having a third opening end open to the storage space and a fourth opening end open to the ring shape vaporization space; and   a liquid fuel composition contained in the storage space, comprising a liquid fuel and an ignition promoter which provides a vapor pressure in the storage space,
 
whereby the vapor pressure drives the liquid fuel composition to be delivered out the storage space through the second pipeline, vaporized in the ring shape vaporization space and then delivered by the first pipeline to the burner assembly.

This application claims priority to Taiwan Patent Application No.101210029 filed on May 25, 2012 and Taiwan Patent Application No.102114174 filed on Apr. 22, 2013.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid fuel combustion system.Specifically, the present invention relates to a liquid fuel combustionsystem comprising easily ignitable liquid fuel composition.

2. Descriptions of the Related Art

In general, the heat source of a cooking stove is electricity or thecombustion of either natural gas (hereinafter referred to as “NG”) orliquefied petroleum gas (hereinafter referred to as “LPG”). An electriccooking stove although is capable of providing a clean heat sourcewithout any CO₂ emission, it has the shortcomings of low heat transferrate and poor homogeneity of heat distribution. The NG or LPG fueledstove is a relatively popular choice for most people for its easyoperation and relatively steady heating quality. NG is a convenientcooking fuel source for users located in the network of NG pipelinesystem. However, in many remote area or developing countries, it is toocostly to have a NG supply network facility. As a result, in manycountries, LPG becomes the most popular cooking fuel. But even LPG canbe conveniently transported by storing LPG in a storage tank, it is notonly expensive but also explosive when being leaked into air.

Because of LPG's high cost and potential explosion hazard, numerousattempts have been tried to develop a liquid fueled cooking stove suchas a kerosene or methanol cooking stove. However, none of them can beoperated as convenience as a LPG stove because of the following reasons.First, the liquid fuel cannot be conveniently delivered to the stovefrom its storage tank, and usually require an additional air pump orcompressor or other driving force (e.g., hanging the storage tank at anelevation to provide enough gravitation force to force the fuel to flowto the stove). But the use of the air compressor/pump will put theliquid fuel in an explosive danger because of low explosion limit. Forexample, when using methanol as a liquid fuel, the air blended liquidfuel tends to explode if the methanol concentration in the air blendedliquid fuel falls into the explosion limit of 4% to 65%. The secondreason giving rise to the fail of the liquid fueled cooking stove isthat, the flash point of liquid fuel (e.g., kerosene or methanol) is toohigh to be easily ignited. As a result, the liquid fuels cannot beignited with an electronic igniter; they must be ignited using an “openflame” such as a flame torch or butane gun. Furthermore, a liquid fueledstove usually uses a fiber string to suck up the liquid fuel bycapillary force to the burner section. In the case of kerosene stove,owing to its high flash point range (120° C. to 300° C.), thevaporization of kerosene is slow and difficult; this results in oilysmell and smoke during burning. As to the methanol stove, the methanolflame during burning is unsteady and jumpy.

In this regard, the present invention provides a liquid fuel combustionsystem with high thermal efficiency, which requires no air pump orcompressor to deliver the liquid fuel and comprises an easily ignitableliquid fuel composition that can be easily ignited using an electricigniter without the needs of open flame.

SUMMARY OF THE INVENTION

The primary objective of this invention is to provide a liquid fuelcombustion system, comprising:

-   -   a combustion stove, comprising:        -   a vaporization unit with a ring shape vaporization space;        -   a burner assembly, comprising a burning head, a first jet            opening, and a burning tube connecting the burning head to            the first jet opening, wherein the burning tube has at least            one air opening; and        -   a first pipeline, having a first opening end open to the            ring shape vaporization space and a second opening end open            to the first jet opening;    -   a liquid fuel storage tank, having a storage space;    -   a second pipeline, having a third opening end open to the        storage space and a fourth opening end open to the ring shape        vaporization space; and    -   a liquid fuel composition contained in the storage space,        comprising:        -   a liquid fuel selected from the group consisting of C1-C4            alcohols, liquid hydrocarbons and combinations thereof; and        -   an ignition promoter, which is a high volatile hydrocarbon            having a flash point lower than the liquid fuel and provides            a vapor pressure in the storage space, wherein the amount of            the ignition promoter is at least about 1 wt % based on the            weight of the liquid fuel,            whereby the vapor pressure composition drives the liquid            fuel to be delivered out the storage space through the            second pipeline, vaporized in the ring shape vaporization            space and then delivered by the first pipeline to the burner            assembly.

The detailed technology and preferred embodiments implemented for thesubject invention are described in the following paragraphs accompanyingthe appended drawings for people skilled in this field to wellappreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing one embodiment of the liquid fuelcombustion system according to the present invention;

FIG. 2 is a schematic diagram showing one embodiment of the combustionstove of the liquid fuel combustion system according to the presentinvention;

FIG. 3 is a schematic diagram showing another one embodiment of thecombustion stove of the liquid fuel combustion system according to thepresent invention;

FIG. 4 is a schematic diagram showing yet another one embodiment of thecombustion stove of the liquid fuel combustion system according to thepresent invention;

FIG. 5A is a schematic diagram showing one embodiment of the burninghead of the combustion stove;

FIG. 5B is a schematic diagram showing another one embodiment of theburning head of the combustion stove;

FIG. 5C is a schematic diagram showing yet another one embodiment of theburning head of the combustion stove;

FIG. 5D is a schematic diagram showing yet another one embodiment of theburning head of the combustion stove;

FIG. 6 is a schematic diagram showing one embodiment of the combustionstove comprising a plurality of burner assemblies;

FIG. 7 is a schematic diagram showing another one embodiment of theliquid fuel combustion system according to the present invention; and

FIG. 8 is a schematic diagram showing yet another one embodiment of theliquid fuel combustion system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, some embodiments of the present invention will be describedin detail with reference to the appended drawings. However, withoutdeparting from the spirit of the present invention, the presentinvention may be embodied in various embodiments and should not belimited to the embodiments described in the specification and drawings.Furthermore, for clarity, the size of each element and each area may beexaggerated in the appended drawings and not depicted in its actualproportion. Unless it is additionally explained, the expressions “a,”“the,” or the like recited in the specification of the present invention(especially in the claims) should include both the singular and theplural forms.

Referring to FIG. 1, which shows an embodiment of the liquid fuelcombustion system according to the present invention, the liquid fuelcombustion system comprises:

-   -   a combustion stove 1, comprising a vaporization unit 11 with a        ring shape vaporization space 12, a burner assembly 13 and a        first pipeline 14 connecting the vaporization unit 11 to the        burner assembly 13;    -   a liquid fuel storage tank 21 having a storage space 22;    -   a second pipeline 23, having a third opening end 231 open to the        storage space 22 and a fourth opening end 232 open to the ring        shape vaporization space 12; and    -   a liquid fuel composition (not shown) contained in the storage        space 22.

According to the invention, the liquid fuel composition comprises aliquid fuel and an ignition promoter, wherein the ignition promoter is ahigh volatile hydrocarbon having a flash point lower than the liquidfuel and provides a vapor pressure in the storage space 22, whereby thevapor pressure drives the liquid fuel composition to be delivered outthe storage space 22 through the second pipeline 23, vaporized in thering shape vaporization space 12 and then delivered by the firstpipeline 14 to the burner assembly 13 for combustion use.

Then referring to FIG. 2, which shows an embodiment of the combustionstove according to the present invention, the vaporization unit 11 isprovided with a ring shape vaporization space 12, which provides asufficient surface area for the liquid fuel delivered thereinto to beheated and vaporized. That is, the ring shape vaporization space 12provides a buffering space for the vaporization of liquid fuel, smoothesthe flow of the liquid fuel composition, and solves the flickeringproblem of flame. Besides, the vaporization unit 11 is disposed aroundand preferably above the burner assembly 13 to use the heat generatedduring the burning at the burner assembly 13 to vaporize the liquid fuelcomposition in the ring shape vaporization space 12.

According to the present invention, there is no special limitation onthe appearance of the ring shape vaporization space 12. For example, thering shape vaporization space 12 may be formed in a hollow disc shape(see FIG. 2) or a hollow bowl shape expanding up- and outward (see FIG.3 or 4). In the hollow-disc-shaped vaporization space of FIG. 2, thering shape vaporization space 12 has a thickness T₁ and a planar widthW₁; and in the hollow-bowl-shaped vaporization space of FIG. 3 or 4, thering shape vaporization space 12 has a thickness T₂/T₃ and a slopelength L₁/L₂ and an outward expanding tilt angle α₁/α₂. Generally, inthe case of being formed in a hollow disc shape, the ring shapevaporization space 12 has a thickness of about 2 mm to about 8 mm,preferably about 3 mm to about 6 mm, and a planar width of about 10 mmto about 90 mm, preferably about 30 mm to about 50 mm; and in the caseof being formed in a hollow bowl shape, the ring shape vaporizationspace 12 has a slope length of about 20 mm to about 60 mm, preferablyabout 30 mm to about 50 mm, a thickness of about 2 mm to about 8 mm,preferably about 3 mm to about 6 mm, and an outward expanding tilt angleof about 15 degree to about 40 degree, preferably about 20 degree toabout 35 degree.

Again referring to FIG. 2, the burner assembly 13 comprises a burninghead 131, a burning tube 132 and a first jet opening 133, wherein theburning tube 132 connects the burning head 131 to the first jet opening133 and has at least one air opening 134. After being vaporized in thering shape vaporization space 12 of the vaporization unit 11, the fuelflows through the first jet opening 133 of the burner assembly 13 tothereby reduce the pulse caused by the vaporization of the liquid fuelsuch that the fuel gas flow can be delivered stably and the flickeringproblem of flame can be solved. After passing through the first jetopening 133, the vaporized liquid fuel composition enters the burningtube 132. The burning tube 132 has at least one, preferably 2 to 6, airopening(s) 134 on the wall to suck air into the burning tube 132. Thevaporized liquid fuel will mix with air in the burning tube 132, andthen enters the scattering holes of burning head 131 to be ignited. Theair opening 134 usually has an inner diameter of about 3 mm to about 6mm. In some embodiments of the present invention, as shown in FIG. 2,there are four air openings 134 on the wall of the burning tube 132.

As shown in FIG. 4, the lower part of the vaporization unit 11 could beconnected with an apron 121 to shade the possible splashing of liquidfuel composition. In the case where an apron 121 is applied to shade thepossible splashing of the fuel, the outward tilting angle β of apron 121should be ≦15 degree and the slope length L₃ thereof should be wellcontrolled so as to prevent the apron 121 from shading the air opening134 and generating turbulent air flow. Generally, the slope length L₃ ofapron 121 is about 15 mm to about 35 mm, preferably about 25 mm to about35 mm; and the angle β of apron 121 is about 5 degree to about 15degree, preferably about 10 degree to about 15 degree. Preferably, theburning head 131 is disposed at the connection of the vaporization unit11 and apron 121; and the distance between the apron 121 and burninghead 131 is about 3 mm to about 10 mm, preferably about 5 mm to about 10mm.

According to the present invention, there is no special limitation onthe types of the burning head 131. Any burning head having scatteringholes, such as a burning head with monocyclic holes (see FIG. 5A, theburning head is provided with holes 1311 as the scattering holes),hollow disc type burning head with multi-cyclic pores (see FIG. 5B andFIG. 5C, the burning head is provided with pores 1312 as the scatteringholes), or plate type burning head (see FIG. 5D, the burning head isprovided with pores 1312 as the scattering holes), may be adopted.Furthermore, according to the present invention, a catch-plate may bedisposed beneath the burning head to catch the overflowing fuel.

As shown in FIG. 2, the first pipeline 14 of the combustion stove 1 hasa first opening end 141 open to the ring shape vaporization space 12 anda second opening end 142 open to the first jet opening 133. Preferably,the combustion stove 1 further comprises a second jet opening 15installed in the first pipeline 14. The second jet opening 15 is helpfulto the fuel delivery. In this embodiment, the first pipeline 14 has afirst inner diameter D1 at the section from the first opening end to thesecond jet opening and a second inner diameter D2 at the section fromthe second opening end to the second jet opening, and D1>D2. Throughsuch design, the liquid fuel composition can be delivered stably forsatisfactory combustion. In some embodiments of the present invention,D1 is more than 1 mm and not more than 8 mm and D2 is not less than 1 mmand not more than 5 mm.

According to the present invention, the number of the burner assemblycan be chosen depending on users' needs. In the case where a pluralityof burner assemblies is disposed, each burner assembly comprises aburning head, a burning tube and a first jet opening. For example, FIG.6 shows an embodiment of a combustion stove having three burnerassemblies, wherein the first pipeline has three second opening ends1421, 1422 and 1423 individually open to one of the first jet openings1331, 1332 and 1333 and a multi-direction manifold comprising threeseparate tubes 1431, 1432 and 1433.

It should be noted, there is no special limitations on the material ofthe vaporization unit, apron or relevant pipelines except that thematerial should have a good thermal conductivity. The examples of saidmaterial include aluminum, copper, brass and other copper alloys, andstainless steel.

In the liquid fuel combustion system of the invention, the ring shapevaporization space of the vaporization unit provides a relatively bigspace to facilitate the preheating and vaporization of the liquid. Thisarrangement can avoid generating a discontinuous plug flow, which occursowing to the imperfect vaporization of liquid fuel and results inunstable flame and imperfect combustion. In addition, in the case wherean apron is provided beneath the ring shape vaporization space, it makesflame more concentrate and facilitates the air suction. The improved airsuction enhances the combustion-assisting effect and thus provides arelatively perfect combustion.

Regarding the liquid fuel storage tank of the liquid fuel combustionsystem of the invention, it is used to contain the liquid fuelcomposition. As shown in FIG. 2, the liquid fuel storage tank 21 mayoptionally comprise a feed opening 211 with a cover 213 for thesupplement of the liquid fuel composition. The material of the liquidfuel storage tank 21 is not particularly limited. For example, theliquid fuel storage tank 21 may be made of a usual steel material. Thefluid delivery system and kit disclosed in TW I314970 may be used as theliquid fuel storage tank of the liquid fuel combustion system of theinvention, the contents of which are herein incorporated by reference inits entirety.

Regarding the second pipeline of the liquid fuel combustion system ofthe invention, it has a third opening end open to the storage space anda fourth opening end open to the ring shape vaporization space, wherebythe liquid fuel contained in the storage space of the liquid fuelstorage tank can be delivered to the ring shape vaporization space ofthe vaporization unit. The third opening end of the second pipeline maybe installed within the storage space, e.g., at a position approachingthe bottom of the storage space. For example, referring to FIG. 1, thethird opening end 231 of the second pipeline 23 can be inserted into thestorage space 22 from top to a position of about 1 cm or about 2 cm fromthe bottom. Of course the third opening end 231 of the second pipeline23 can be inserted into the storage space 22 from the bottom as well.Furthermore, as shown in FIG. 1, the liquid fuel combustion system mayfurther comprise a control element 24 installed on the second pipeline.For example, but not limited thereto, the control element 24 may be aflow control element, such as a needle valve, capable of opening theliquid fuel composition flow or adjusting the flow of liquid fuel, orjust an on/off switch. In this case, the liquid fuel composition may beignited with an electric igniter (not shown) around the burning head 131after the control element 24 is opened. FIG. 7 shows another embodimentsof the liquid fuel combustion system of the invention, where the controlelement 24 is an ignition switch with flow control function, itcomprises an electric igniter 241 (such as a lighter flint) and a wire242 connecting the electric igniter 241 to the control element 24. Inthis case, when the control element 24 is opened, the liquid fuelcomposition passes through the control element 24 and enters thecombustion stove 1, and at the same time, the electric igniter 241provides an electric arc to ignite the fuel coming out from the burninghead 131. After igniting the fuel, the strength of the generated flamecan be adjusted by the control element 24. The control element 24 hereis commercially available. For example, it can be obtained by narrowingthe diameter (e.g., to 0.08 mm to 1 mm) of gas outlet of gas stove soldin the market.

According to the present invention, the second pipeline 23 may furthercomprises a fifth opening end 233 being set below the air opening 134and above a catch-plate 27 and equipped with an ignition unit 25, asshown in FIG. 8. Once the ignition unit 25 is started, the liquid fuelcomposition passes through the ignition unit 25 and enters thecatch-plate 27, and meanwhile, the ignition unit 25 provides an electricarc to ignite the liquid fuel composition on the catch-plate 27. At thistime, opening the control element 24 (a flow control element in thiscase) to make the liquid fuel composition enters the ring shapevaporization space 12, and the entered liquid fuel composition could bevaporized by absorbing the heat from the flame on the catch-plate 27.Usually, there will be a shutter 26 being disposed on the catch-plate 27to concentrate the liquid fuel composition came from the ignition unit25 to facilitate the ignition. The height of the shutter 26 should becontrolled to prevent the shutter 26 from shading the air opening 134and thus generating turbulent air flow. Similarly, the ignition unit 25could be obtained from the gas stove sold in the market too.

Furthermore, in some embodiments of the present invention, the secondpipeline 23 tilts downward to open to the ring shape vaporization space12 as shown in FIG. 1. This is helpful in providing a relatively stablecombustion.

According to the present invention, the storage space 22 contains aliquid fuel composition comprising a liquid fuel and an ignitionpromoter. The ignition promoter is a high volatile hydrocarbon having aflash point lower than the liquid fuel. “High volatile hydrocarbon” heremeans a hydrocarbon with a vapor pressure of about 15 kpa at standardstate (20° C. and 1 atm). The ignition promoter makes the liquid fuelcomposition can be easily and quickly ignited. This allows the liquidfuel combustion system of the invention to use an electric igniterrather than open fire to ignite the liquid fuel composition and thusmakes the system much safer. Specifically, it is known that the in thecase of igniting a liquid fuel, the vapor concentration of the liquidfuel must be higher than its lower flammability limit (LFL) and thevapor must be heated to a temperature higher than its auto-ignitiontemperature. However, in general ambient temperature, it usually takes along time to generate sufficient vapor concentration of liquid fuel; andthus, the ignition of liquid fuel usually takes a quite long time. Forexample, in the case of methanol, it takes about 30 sec to about 50 secto generate sufficient vapor concentration to ignite methanol. Theinventors found that the ignition promoter can significantly shorten theignition time of liquid fuel. Without being bound to theory, it isbelieved that the ignition promoter slightly dissolves in the liquidfuel and forms a uniform liquid fuel composition; and after beingdelivered to the combustion stove, the dissolved ignition promoter caneasily vaporized into vapor and reach its LFL. As a result, the liquidfuel composition can be quickly ignited without the needs of reachingthe LFL of liquid fuel (e.g., methanol) itself.

Furthermore, since the ignition promoter is a high volatile hydrocarbon,it provides a vapor pressure in the storage space, whereby the vaporpressure drives the liquid fuel composition to be delivered to theburner assembly. Specifically, referring to FIG. 1 again, the vaporpressure of ignition promoter drives the liquid fuel composition to bedelivered out the storage space 22 through the second pipeline 23,vaporized in the ring shape vaporization space 12 and then delivered bythe first pipeline 14 to the burner assembly 13. Although we have knownthat the insoluble gas (such as air, nitrogen or hydrogen) can beinstalled into a liquid fuel storage tank to provide a driving pressure.The insoluble gas, however, is different from the ignition promoter inthe present invention and cannot be partially solved into the liquidfuel to promote the ignition of liquid fuel. In the case of using theinsoluble gas to provide a driving pressure, with the consumption of theliquid fuel, the fuel level in the storage tank is decreased, the volumeover the liquid face is increased, and the driving pressure is thusdecreased (P=nRT/V). In contrast, in the case of the liquid fuelcomposition according to the present invention, when the fuel level inthe storage tank is decreased and the volume of the space over theliquid face is increased, the ignition promoter dissolved in the liquidfuel will be vaporized and the generated vapor thus maintains thepressure in the storage tank substantially constant.

In practical use of the liquid fuel combustion system of the invention,if the vaporization unit is not heated in advance, the liquid fuelcomposition in the vaporization unit and first pipeline is substantiallyin a form of a gas liquid mixture at the beginning. After the gas liquidmixture being delivered into the burning head and ignited, the liquidfuel composition in the ring shape vaporization space will start to bewell vaporized through the heat provided by the combustion. Therefore,at the beginning, a small fraction of non-vaporized liquid fuelcomposition may be splashed from the air opening or burning head. Toshade the possible splashing, the apron as described above may bedisposed below the vaporization unit, whereby the splashed fuel willdrop along the apron to the bottom of catch-plate to avoid potentialrisk.

According to the present invention, the liquid fuel is selected from thegroup consisting of C1-C4 alcohols, liquid hydrocarbons (e.g., C5-C12hydrocarbons) and combinations thereof. For example, the liquid fuel maybe methanol, ethanol, heptane, octane, cleaning naphtha, kerosene,diesel and the like. In some embodiments of the present invention, theliquid fuel is methanol or cleaning naphtha. As to the ignitionpromoter, it can be any high volatile hydrocarbons having a flash pointlower than the liquid fuel. Generally, the solubility of the ignitionpromoter in the liquid fuel is preferably at least 1 wt % based on theweight of the liquid fuel. For example, the ignition promoter may beselected from the group consisting of liquefied petroleum gas (LPG),propane, butane, pentane, hexane, petroleum ether, dimethyl ether andmixtures thereof. Preferably, the ignition promoter is LPG (flash point:−60° C., standard state), butane (flash point: −60° C., standard state),or the combinations thereof. In some embodiment of the presentinvention, the ignition promoter is LPG. As to the amount of theignition promoter, it depends on the species of ignition promoter,operating pressure, ambient temperature, and the like. For example, ifthe flash point of ignition promoter is relatively low or the ambienttemperature is relatively high, a relatively small amount of ignitionpromoter is required; and if the ambient temperature is relatively low,the amount of ignition promoter should be increased. Of course theamount of ignition promoter should be sufficient to provide desiredrapid ignition benefits, but it is also found that if the amount ofignition promoter is overhigh, it will not only increase the cost butalso lead to an incomplete combustion. In view of this, according to thepresent invention, the amount of the ignition promoter is at least about1 wt % and usually in an amount ranging from about 1 wt % to about 8 wt% based on the weight of the liquid fuel. In some embodiments of thepresent invention, the ignition promoter is in an amount ranging fromabout 4 wt % to about 8 wt % based on the weight of the liquid fuel.

Furthermore, since the flash point of the ignition promoter of theliquid fuel composition is lower than that of the liquid fuel, once theliquid fuel composition being delivered to the burning head, thevaporization speed of the liquid fuel is slower than that of theignition promoter. As a result, the flame's strength may become unstableespecially in a high ambient temperature. To solve this question, theinventor found that a material having a polarity between the liquid fueland ignition promoter may be added into the liquid fuel composition as astabilizer, which can stabilize the ignition promoter within the liquidfuel and stabilize the flame strength. Therefore, according to thepresent invention, the liquid fuel composition may further comprise astabilizer. Without being bound to theory, it is believed that thestabilizer acts as an assistant or a bridge that facilitates thedissolution of ignition promoter in the liquid fuel and thus, can keepthe ignition promoter from losing when the ambient temperature/pressurechanges. For example, according to the check of the inventor, if 5 wt %(based on the weight of methanol) LPG is added into methanol, the gaugepressure of LPG vapor pressure is about 1.5 kg/cm²; and if a few amountof acetone is further added into the mixture of LPG and methanol, thegauge pressure of LPG vapor pressure is lowered to about 1.25 kg/cm².This manifests that acetone enhances the stability of LPG in methanoland the dissolution of LPG.

The stabilizer may be ketone(s), ether(s), a polymer with a molecularweight of less than about 5,000 Dalton, or combinations thereof.Specifically, the stabilizer may be selected from the group consistingof acetone, methyl ethyl ketone (MEK), dimethyl ether (DME), diethyleneglycol (DEG), polyethylene glycol (PEG) with a molecular weight of lessthan about 5,000 Dalton, a polymer with a molecular weight of less thanabout 5,000 Dalton and having one or more hydrophilic functional groupin its main chain (such as polyallyl alcohol), and combinations thereof.The hydrophilic functional group here is selected from the groupconsisting of an ether group, an ester group, an amino, a carboxyl(—COOH), a thiol (—SH) and combinations thereof. In some embodiments ofthe present invention, the stabilizer is acetone and/or MEK. Althoughthe amount of the stabilizer should be sufficient to provide desiredstabilizing, it is found that if the amount of stabilizer is overhigh,it may not only increase the cost but also affect the comburent effect.In view of this, according to the present invention, the amount of thestabilizer is in an amount of not higher than about 5 wt % based on theweight of the liquid fuel. Generally, the stabilizer is in an amountranging from about 0.5 wt % to about 5 wt %, preferably from about 1 wt% to about 3 wt %. Besides, since the loss of ignition promoter in a lowambient temperature (e.g., in frigid zone) is relatively low, the amountof stabilizer can be reduced in this circumstance.

In addition to the ignition promoter and stabilizer, according to thepresent invention, the liquid fuel composition may further comprise aheat transfer promoter. It is known that the liquid fuel will beoxidized to water vapor and carbon dioxide after being ignited. Whenusing the liquid fuel to heat a cooking pot, the gas flow (generatedowing to the oxidization of liquid fuel) will form a thin layer at thebottom of the cooking pot (i.e., between the flame and the cooking pot).As a result, the higher the thermal conductivity of the thin layer, thebetter the thermal efficiency of the liquid fuel to the cooking pot. Theinventor found that, the thermal efficiency of the liquid fuel can beimproved by adding a heat transfer promoter to enhance the net thermalconductivity of the gas flow that forms the thin layer. The species ofheat transfer promoter is not particularly limited but usually, it issoluble to the liquid fuel and easily to be vaporized, has a highthermal conductivity and barely remains on the cooking pot. In view ofthis, suitable heat transfer promoter may be a high thermal conductivematerial with a thermal conductivity of about 0.2 W/M-K to about 0.65W/M-K and soluble to the liquid fuel. Preferably, the heat transferpromoter is selected from the group consisting of ethylene glycol,glycerol, ethylene diamine, water and combinations thereof. In someembodiments of the present invention, the heat transfer promoter iswater.

To avoid the heat transfer promoter consuming too much heat releasedfrom the liquid fuel composition and thus lowering the thermalefficiency, the amount of the heat transfer promoter should becontrolled. For example, in the case where the liquid fuel is methanoland the heat transfer promoter is water, water's vaporization heat(2,367 kJ/kg at 300 K) is almost thrice as high as methanol'svaporization heat (1,180 kJ/kg at 300 K), therefore we should avoid thevaporization of water consuming too much heat released by methanol andthus lowering the thermal efficiency. Therefore, the amount of the heattransfer promoter is usually from about 1 wt % to about 15 wt %,preferably from about 3 wt % to about 10 wt %, based on the weight ofthe liquid fuel. In the suggested amount, the heat transfer promoter canenhance the heat exchanger between the flame and the cooking pot whilenot consuming too much heat for its vaporization.

Moreover, the inventor also found that the ignition time of liquid fuelcomposition can be further shortened when using high thermal conductiveliquid such as ethylene glycol, glycerol or water as the heat transferpromoter. Without being restricted by theories, it is believed that thesolubility of ignition promoter is lowered in the presence of heattransfer promoter and the lower solubility facilitates the vaporizationof ignition promoter after the liquid fuel composition being deliveredto the burning head and thus shortens the ignition time.

Given the above, the liquid fuel combustion system has at least thefollowing features: the system requires no air pump or compressor andthus is easy to carry; the liquid fuel composition can be easily ignitedwithout the use of an open flame; and the designation of the combustionstove (the ring shape vaporization space, and the inner diameter of thefirst pipeline) makes the liquid fuel flow smooth and solves theflickering problem of flame.

Hereinafter, the present invention will be described in more detail withreference to the following Examples, but the scope of the presentinvention is not limited thereto.

EXAMPLES

According to the ratio indicated in Tables 1 to 6, the liquid fuel(methanol or cleaning naphtha) or the mixture of the liquid fuel andstabilizer and/or heat transfer promoter were loaded into the storagespace of liquid fuel storage tank to provide liquid fuel compositions,and a predetermined amount of ignition promoter was then added into thestorage space. The liquid fuel storage tank was then shaken to uniformlymix the components of liquid fuel composition. The pressure of theliquid fuel storage tank was measured and recorded in the tables.

Thereafter, the flow rate of liquid fluid composition was controlled inthe range of about 10 g/min to about 20 g/min. An electric igniter wasdisposed adjacent to the burning head to provide an arc to ignite theliquid fuel composition. The required time period to ignite the liquidfuel composition while obtain a steady flame strength (ignition time θ)was measured and recorded in the tables respectively. After obtainingthe steady flame strength, a cooking pot filled with water was disposedabove the combustion stove of liquid fuel combustion system for heating.

The real combustion heat Qc (unit: kJ) provided for heating W kg waterfrom initial temperature T₀° C. to 95° C. is calculated by the followingequation:

Qc=F*ψ*ΔH

wherein, W=2; F is the flow rate of liquid fuel composition; ψ is thetime required for raising the water temperature from T₀ (initialtemperature) to 95° C.; ΔH is the liquid fuel composition's combustionheat (unit: kJ/kg), and the combustion heat of the liquid fuel andignition promoter are as follows:

LPG: 46,100

butane: 49,600

MEK: 33,890

cleaning naphtha: 44,940methanol: 19,940methanol with 4 wt % LPG dissolved therein: 20,980methanol with 8 wt % LPG dissolved therein: 22,030methanol with 4 wt % butane dissolved therein: 21,126cleaning naphtha with 8 wt % LPG dissolved therein: 45,033methanol with 2 wt % water and 4 wt % LPG dissolved therein: 20,560methanol with 4 wt % water and 4 wt % LPG dissolved therein: 20,140methanol with 8 wt % water and 4 wt % LPG dissolved therein: 19,300methanol with 1 wt % MEK and 4 wt % LPG dissolved therein: 20,277

The theoretical combustion heat Qt (unit: kJ) required for heating W kgwater from T₀° C. to 95° C. is calculated by the following equation:

Qt=Cp*(95−T ₀)*W

wherein, Cp=4.1868 kJ/kg·K; W is the weight of water (unit: kg); T₀ isthe initial temperature of water.

The relevant results were listed in the following Tables 1 to 7, whereinthe thermal efficiency η=Qt/Qc.

TABLE 1 Influence of ignition promoter methanol + methanol + 4 wt %butane 4 wt % LPG methanol pressure (atm) 1.2 0.75 0.75 pressure sourcebutane LPG nitrogen ignition time θ (sec) 4.5 5 >120, No flame heatingtime ψ (sec) 391.8 401 459 power (kW) 3.48 3.28 3.13 thermal efficiencyη (%) 47.4 47.7 44.8 Note The liquid fuel was delivered by nitrogen.

TABLE 2 Influence of ignition promoter cleaning naphtha + 8 wt % LPGcleaning naphtha pressure (atm) 1.6 1.6 pressure source LPG nitrogenignition time θ (sec) 1.2 3.1 heating time ψ (sec) 483 494 power (kW)2.65 2.72 thermal efficiency η 43.8 42.7 (%) Note The liquid fuel wasdelivered by nitrogen.

TABLE 3 Influence of the amount of ignition promoter methanol +methanol + 4 wt % LPG 8 wt % LPG pressure (atm) 0.75 0.95 pressuresource LPG LPG ignition time θ (sec) 5 6.5 heating time ψ (sec) 401.7399.1 power (kW) 3.28 3.51 thermal efficiency η (%) 47.7 43.3 Note Thecombustion was too heavy.

TABLE 4 Influence of heat transfer promoter methanol + methanol + 4 wt %LPG + 4 wt % LPG 4 wt % water pressure (atm) 1.25 1.55 pressure sourceLPG LPG ignition time θ (sec) 1.81 1.75 heating time ψ (sec) 402 402power (kW) 3.47 3.53 thermal efficiency η (%) 46.2 45.4 Note Thepressure in the liquid fuel storage tank was raised.

TABLE 5 Influence of the amount of heat transfer promoter methanol +methanol + methanol + 4 wt % LPG + 4 wt % LPG + 4 wt % LPG + 2 wt %water 4 wt % water 8 wt % water pressure (atm) 1.4 1.55 2.15 pressuresource LPG LPG LPG ignition time θ 3.87 1.75 0.85 (sec) heating time ψ394 402 422 (sec) power (kW) 3.60 3.53 3.30 thermal 46.5 47.3 50.3efficiency η (%)

TABLE 6 Influence of stabilizer methanol + methanol + 4 wt % LPG + 4 wt% LPG 1 wt % MEK pressure (atm) 0.95 0.82 pressure source LPG LPGignition time θ 4.3 2.0 (sec) heating time ψ 482 379 (sec) power (kW)3.62 4.24 thermal efficiency 35.8 38.02 η (%)

As shown in Tables 1 to 6, the ignition promoter is help to the ignitionof liquid fuel (methanol/cleaning naphtha); the stabilizer can stabilizethe ignition promoter and thus is helpful to obtain a smooth combustion(steady flame strength); and the heat transfer promoter can improve thethermal efficiency of liquid fuel.

Hereinafter, the effect of stabilizer (MEK) on the pressure of vapor LPGwas measured and tabulated in the following Table 7.

TABLE 7 Influence of stabilizer on pressure methanol + methanol + 4 wt %LPG + 4 wt % LPG 2 wt % MEK time pressure fuel pressure fuel (sec)(kg/cm²) consumption (g) (kg/cm²) consumption (g) 0 2.4 1 2.0 0 30 2 7.91.6 6.5 60 1.8 15.28 1.45 12.93 90 1.6 15.28 1.4 19.9 120 1.5 22.5 1.329 150 1.4 30.38 1.2 36.02 180 1.4 36.98 1.1 43.33 210 1.3 43.01 1.0550.35 240 1.25 49.75 1 57.9 270 1.2 57.56 1 65.02 300 1.1 65.49 0.95 73330 1.05 73.2 0.9 80.65 360 1 81.2 0.9 86.73 390 0.95 89.35 0.85 93.95420 0.9 93.56 0.8 100.01

As shown in FIG. 7, the LPG pressure in the tank decreased with theconsumption of methanol. However, in the case where 2 wt % stabilizer(MEK) was used, the decrease of pressure was lowered. This manifeststhat stabilizer is helpful to stabilize the pressure of ignitionpromoter. As a result, the ignition promoter can maintain a moreconcentration in methanol to help the consumption.

Furthermore, the solubility and pressure of LPL in methanol and MEK weremeasured to observe the effect of the stabilizer on stabilizing LPGvapor. The result was tabulated in the following Table 8.

TABLE 8 Solubility and pressure of LPG in methanol and MEK LPG/100 gLPG/100 g methanol MEK pressure solubility pressure solubility kg/cm²g/100 g kg/cm² g/100 g 1.61 0.91 1.68 1.47 2.62 2.76 2.2 2.84 3.19 3.832.89 4.88 3.68 4.77 3.53 6.86 4.55 6.44 3.9 7.93 5 7.35 4.45 9.55 4.7510.57 5.02 11.3

As shown in FIG. 8, under the same pressure, the solubility of LPG inMEK is relatively high. This further manifests the stabilizing effect ofMEK.

The liquid fuel compositions were prepared according to Table 9 and theignition time of the liquid fuel compositions and the influence ofdifferent stabilizers are respectively measured and tabulated in Table9.

TABLE 9 Effect of different stabilizers to the LPG in methanolcomponents methanol + methanol + methanol + (%) methanol MEK DEG-100PEG-500 methyl 96 95 95 95 LPG 4 4 4 4 MEK 0 1 0 0 DEG 0 0 1 0 PEG 0 0 01 Results ignition time 2.5 2.0 1.8 1.8 (sec) residue of the none nonenone none combustion pressure variation in discharged dischargeddischarged discharged the liquid fuel percentage pressure percentagepressure percentage pressure percentage pressure storage tank (%) (atm)(%) (atm) (%) (atm) (%) (atm) 0 0.95 0 0.82 0 0.81 0 0.8 3 0.75 7 0.7 70.7 7 0.7 7 0.7 13 0.65 13 0.65 17 0.7 13 0.65 27 0.6 23 0.6 53 0.65 470.62 47 0.6 33 0.55 90 0.6 70 0.58 60 0.6 50 0.55 93 0.58 90 0.5 77 0.5886 0.5 100 0 100 0 90 0.55 100 0 97 0.53 100 0

As shown in Table 9, the listed stabilizers all provide stabilizingeffects (the decrease of pressure was lowered).

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in this field may proceedwith a variety of modifications and replacements based on thedisclosures and suggestions of the invention as described withoutdeparting from the characteristics thereof. Nevertheless, although suchmodifications and replacements are not fully disclosed in the abovedescriptions, they have substantially been covered in the followingclaims as appended.

What is claimed is:
 1. A liquid fuel combustion system, comprising: acombustion stove, comprising: a vaporization unit with a ring shapevaporization space; a burner assembly, comprising a burning head, afirst jet opening, and a burning tube connecting the burning head to thefirst jet opening, wherein the burning tube has at least one airopening; and a first pipeline, having a first opening end open to thering shape vaporization space and a second opening end open to the firstjet opening; a liquid fuel storage tank, having a storage space; asecond pipeline, having a third opening end open to the storage spaceand a fourth opening end open to the ring shape vaporization space; anda liquid fuel composition contained in the storage space, comprising: aliquid fuel selected from the group consisting of C1-C4 alcohols, liquidhydrocarbons and combinations thereof; and an ignition promoter, whichis a high volatile hydrocarbon having a flash point lower than theliquid fuel and provides a vapor pressure in the storage space, whereinthe amount of the ignition promoter is at least about 1 wt % based onthe weight of the liquid fuel, whereby the vapor pressure drives theliquid fuel composition to be delivered out the storage space throughthe second pipeline, vaporized in the ring shape vaporization space andthen delivered by the first pipeline to the burner assembly.
 2. Thesystem according to claim 1, wherein the ring shape vaporization spaceis formed in a hollow disc shape or a hollow bowl shape expanding up-and outward.
 3. The system according to claim 1, wherein the combustionstove further comprises an apron connected to the lower part of thevaporization unit.
 4. The system according to claim 1, wherein thecombustion stove further comprises a second jet opening installed in thefirst pipeline.
 5. The system according to claim 4, wherein the firstpipeline has a first inner diameter D1 at the section from the firstopening end to the second jet opening and a second inner diameter D2 atthe section from the second opening end to the second jet opening, andD1>D2.
 6. The system according to claim 5, wherein D1 is more than 1 mmand not more than 8 mm and D2 is not less than 1 mm and not more than 5mm.
 7. The system according to claim 1, wherein the inner diameter ofthe air opening ranges from about 3 mm to about 6 mm.
 8. The systemaccording to claim 1, wherein the combustion stove comprises a pluralityof burner assemblies, and each of them comprises a burning head, aburning tube and a first jet opening; and the first pipeline has aplurality of second opening ends individually open to one of the firstjet openings.
 9. The system according to claim 8, wherein the firstpipeline has a multi-direction manifold.
 10. The system according toclaim 1, wherein the third opening end is installed within the storagespace.
 11. The system according to claim 1, which further comprises aflow control element or an ignition switch with flow control functioninstalled on the second pipeline.
 12. The system according to claim 1,wherein the second pipeline further comprises a fifth opening end belowthe air opening and equipped with an ignition unit.
 13. The systemaccording to claim 1, wherein the second pipeline tilts downward to opento the ring shape vaporization space.
 14. The system according to claim1, wherein the ignition promoter is in an amount ranging from about 1 wt% to about 8 wt % based on the weight of the liquid fuel.
 15. The systemaccording to claim 1, wherein the ignition promoter is selected from thegroup consisting of liquefied petroleum gas (LPG), propane, butane,pentane, hexane, petroleum ether, dimethyl ether and mixtures thereof.16. The system according to claim 1, wherein the liquid fuel compositionfurther comprises: a stabilizer being selected from the group consistingof ketone(s), ether(s), a polymer with a molecular weight of less thanabout 5,000 Dalton, and combinations thereof; and a heat transferpromoter being soluble in the liquid fuel and having a thermalconductivity ranging from about 0.20 W/M-K to about 0.65 W/M-K, whereinthe stabilizer is in an amount of not higher than about 5 wt % and theheat transfer promoter is in an amount of not higher than about 15 wt %,based on the weight of the liquid fuel.
 17. The system according toclaim 16, wherein stabilizer is selected from the group consisting ofacetone, methyl ethyl ketone (MEK), dimethyl ether (DME), diethyleneglycol (DEG), polyethylene glycol (PEG) with a molecular weight of lessthan about 5,000 Dalton, a polymer with a molecular weight of less thanabout 5,000 Dalton and having one or more hydrophilic functional groupin its main chain, and combinations thereof; and the heat transferpromoter is selected from the group consisting of ethylene glycol,glycerol, ethylene diamine, water and combinations thereof.
 18. Thesystem according to claim 17, wherein in the polymer with a molecularweight of less than about 5,000 Dalton and having one or morehydrophilic functional group in its main chain, the hydrophilicfunctional group is independently an ether group, an ester group, anamino, a carboxyl (—COOH), or a thiol (—SH).
 19. The system according toclaim 16, wherein the amount of the stabilizer is from about 0.5 wt % toabout 5 wt % and the amount of the heat transfer promoter is from about1 wt % to about 15 wt %, based on the weight of the liquid fuel.
 20. Thesystem according to claim 19, wherein the liquid fuel compositioncomprises about 4 wt % to about 6 wt % LPG as the ignition promoter,about 1 wt % to about 3 wt % methyl ethyl ketone as the stabilizer andabout 3 wt % to about 10 wt % water as the heat transfer promoter, basedon the weight of the liquid fuel; and the liquid fuel is methanol.